Chemistry Journal of Moldova

2010 Volume 5, no.2

THE REACTIONS OF (+)-2- AND (+)-3-CARENES WITH THE RETENTION OF THE BICYCLIC FRAMEWORK

Author(s):

L. Bets, L. Vlad, F. Macaev


Field: Organic chemistry
Type: Review
Issue: 2010 Volume 5, no.2
Pages: 6-23
Keywords: (+)-2- carene, (+)-3-carene, trimethylbicyclo[4.1.0]heptanes, trimethylbicyclo[4.1.0]hept-3-enes, organic synthesis.
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CATALYTIC WAVE OF CHLORATE IONS IN THE PREZENCE OF THE MOLYBDENUM (VI) - 2,3-DIHYDROXYBENZALDEHYDE COMPLEX

Author(s):

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


Field: Analytical chemistry
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 24-29
Keywords: Voltammetry, catalytic current, molybdenum, 2,3-dihydroxybenzaldehyde, potassium chlorate.
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2010.05(2).02

Graphical Abstract:
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 ∆Sa¹= -28.3 e.u. have also been determined.

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THE STUDY OF THE BUFFERING CAPACITY OF SEVERAL WATER OBJECTS IN THE REPUBLIC OF MOLDOVA

Author(s):

Angela Lis, Gheorghe Duca, Elena Bunduchi, Viorica Gladchi, Nelli Goreaceva


Field: Ecological chemistry
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 30-36
Keywords: buffering capacity, acid-base balance, carbon system, humic system, stability to acidification.
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DOI:
dx.doi.org/10.19261/cjm.2010.05(2).03

Graphical Abstract:
The current work represents the estimation of the buffering capacity on the Dniester River waters and its tributaries between November 2008 and October 2009.

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CATALYTIC OXIDATION OF METHYLENE BLUE

Author(s):

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


Field: Ecological chemistry
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 37-40
Keywords: catalytic oxidation, methylene blue, activated carbon.
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2010.05(2).04

Graphical Abstract:
The intact activated carbon CAN-8, obtained from nutshells by activation with water vapours, 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.

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THE POLLUTION SPECTRUM OF OLD PESTICIDES STORAGES IN MOLDOVA

Author(s):

Duca Gh., Bogdevich O., Cadocinicov O., Porubin D.


Field: Ecological chemistry
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 41-46
Keywords: soil pollution, POPs, pesticides.
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2010.05(2).05

Graphical Abstract:
The old pesticide storages in Moldova showed a large quantity of polluted sites. The inventory of POPs polluted sites showed a huge number of extra high polluted sites (more 50,0 mg/kg) which need the first place a remediation or other action to eliminate direct contact with people and animals. The pollution spectrum of POPs is a complex and consists of five groups: DDTs isomers, HCHs isomers, Toxaphene mixture, Chlordane and Heptachlor. The principal groups among these substances are DDTs and HCHs isomers.

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MODIFIED SCREEN-PRINTED CARBON ELECTRODES WITH TYROSINASE FOR DETERMINATION OF PHENOLIC COMPOUNDS IN SMOKED FOOD

Author(s):

V. Dragancea, R. Sturza, M. Boujtita


Field: Food chemistry
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 47-53
Keywords: screen-printed carbon electrode SPCE; biosensor; phenol; tyrosinase; gas chromatography.
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2010.05(2).06

Graphical Abstract:
A screen-printed carbon electrode modified 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 flow 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 flow injection mode using amperometric biosensor. The result showed good correlation with those obtained by flowinjection analysis (FIA).

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STEROIDAL GLYCOSIDES FROM VERONICA CHAMAEDRYS L. PLANTS. THE STRUCTURES OF CHAMAEDROSIDES A, B, C AND E

Author(s):

Alexandra Marchenko, Pavel Kintia, Bożena Wyrzykiewicz


Field: Natural product chemistry and synthesis
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 54-58
Keywords: steroidal glycoside, NMR analysis, Veronica chamaedrys L.
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2010.05(2).07

Graphical Abstract:
The paper reports on the structural elucidation of the four steroidal glycosides, where two are new, isolated from Veronica chamaedrys L. plants for the first time on the basis of extensive spectral analysis, including 2D NMR spectral data and chemical evidences.

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OBSERVATIONS ON THE ANTIOXIDANT ACTIVITY OF NOVEL DIHYDROXYFUMARIC ACID DERIVATIVES

Author(s):

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


Field: Natural product chemistry and synthesis
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 59-67
Keywords: dihydroxyfumaric acid derivatives, DPPH test, antioxidant activity.
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2010.05(2).08

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

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COMPARATIVE KINETICS STUDY OF THE THERMAL AND THERMO-OXIDATIVE DEGRADATION OF A POLYSTYRENE-CLAY NANOCOMPOZITE BY TGA AND DSC

Author(s):

Ion Dranca, Nicon Ungur,Tudor Lupascu, Oleg Petuhov


Field: Physical chemistry and chemical physics
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 68-72
Keywords: degradation; fire resistance; nanocomposites; thermogravimetric analysis (TGA); differential scanning calorimetry (DSC).
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2010.05(2).09

Graphical Abstract:
The methods of thermogravimetry (TGA) and differential scanning calorimetry (DSC) have been used to study the thermal and thermo-oxidative degradation of polystyrene (PS) and a PS-clay nanocomposite. An advanced isoconversional method has been applied for kinertic analysis. Introduction of the clay phase increasers the activation energy and affects the total heat of degradation, which suggests a change in the reaction mechanism. The obtained kinetic data permit a comparative assessment of the fire resistance of the studied materials.

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METALLIC COMPOUNDS IN THE PHASE OF THE RETICULATED IONIC POLYMERS

Author(s):

Vasilii Gutsanu, Constantin Turta, George Filoti


Field: Physical chemistry and chemical physics
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 73-82
Keywords: ion exchangers, Mossbauer spectra, iron, superparamagnetic, complexes, polymer phase.
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2010.05(2).10

Graphical Abstract:
Using the Mossbauer spectroscopy and other physical methods it was demonstrated the presence of different iron 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-, SO42-., n= from 3- to 1+ in the ion-exchange resins (KU-2, AN-31, AV-17, Varian – AD, EDE-10P) after the contact with sulphate of iron(III) solutions at different conditions: type of solvent, temperature, air atmosphere. In special conditions the ultrafine superparamagnetic particles of Fe2O3 have been obtained.

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